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Appendix Physical Chemistry

Physical Quantities: 

In physical science, we commonly deal with quantities such as pressure, volume, mass, temperature, current, etc. These quantities are known as physical quantities. 
A physical quantity has two components, namely, numerical value and its unit and is written as, 
Physical quantity = Numerical value unit
Force = 5 Newton
Here Physical quantity Newton and its numerical value 5
C.G.S Units
Physical quantity Name of the Unit Symbol
Length Centimeter cm
Mass Gram gm
Time Second S
Electric Current Ampere Amp
Temperature Kelvin 0K
S.I Units
Physical quantity Name of the Unit Symbol
Length Meter m
Mass Kilogram Kg
Time Second S
Electric Current Ampere Amp
Temperature Kelvin 0K
Dimension
Physical quantity Name of the Unit
Length L
Mass M
Time T

Definition of Seven Base Physical Quantities:

Metre: The metre is the length of path traveled by light in vacuum during a time interval 1/299 792 458 of a second.
1. Area
Area = Length × Length 
Thus the unit of Area = Unit of Length × Unit of Length 
Unit of Area in C.G.S. System = cm × cm = cm² 
Unit of Area in S.I. System is = m × m =
Dimension of Area = L × L = [L]²
2. Volume
Volume (V) = Length × Length × Length.
Thus the unit of Volume = Unit of Length × Unit of Length × Unit of Length.
Unit of Area in C.G.S. System = cm × cm × cm = cm³ 
Unit of Area in S.I. System is = m × m × m = m³ 
Dimension of Area = L × L × L = [L³]
3. Density
Density (d) = Mass/Volume 
Thus the unit of Area = Unit of Mass/Unit of Volume. 
Unit of Area in C.G.S. System = gm/cm³ = gm cm⁻³ 
Unit of Area in S.I. System is = Kg/ = Kg m⁻³ 
Dimension of Area = [M]/[L³] = [M L⁻³]
4. Force
From the Newton Second Low of MotionForce = Mass × Acceleration. 
or, Force = Mass × Velocity/Time 
or, Force = Mass × (Length/Time) /Time, 
Here Velocity = Length/Time 
or, Force = Mass × (Length/Time²) 
Thus the unit of Force in C.G.S. System, =Unit of Mass × (Unit of Length/Unit of Time²) 
 = gm × cm/sec2 
gm cm/sec2 
or, gm cm sec-2 
or Dyne. 
 Again in the same way Unit of Force in S.I System, 
Kg m/sec2 
or Kg m sec-2 
or Newton. 
From the above discussion dimension of Force, = dimension of Mass × dimension of Length/dimension of Time². 
 Thus the dimension of Force = [MLT-2]
Conversation Newton to Dyne
1 Newton = Kg m/sec2
= (1 Kg× 1 m )/(1 sec)² 
We know that, 1 Kg = 10³ gm and 1 m = 10² cm 
Thus, 1 Newton = (10³gm × 10² cm)/(1 sec)² 
= 10⁵ gm cm/sec2 
105 Dyne
5. Work
We Know that, Work (W) = Force(F) × Displacement(d). 
Thus, the unit Work = unit of Force × unit of Displacement(d) 
∴ Unit of Work in C.G.S. System, = (gm cm/sec2) × cm 
or, gm cm2/sec2 
or, gm cm2sec-2 
or, erg. 
 And unit of work in S.I. system = (Kg m/sec2) × m 
or, Kg m2/sec2 
Kg m2sec-2
or, Joule. 
From the above discussion dimension of Work, = dimension of Mass × {(dimension of Length)²/dimension of Time²}. 
Thus dimension of Work = [ML2T-2]
Conversation Joule to erg
1 Joule = 1 Kg m²/sec² 
= (1 Kg × 1 m² )/1 sec². 
We know that, 1 Kg = 10³ gm and 1 m = 10² cm. 
Thus, 1 Joule = {10³ gm × (10²)² cm}/1 sec² 
= 10⁷ gram cm²/sec² 
= 10⁷ erg.
6. Work
The ability to doing work is termed as Energy. Thus, the unit and dimension of energy and work is same. 
Unit of Energy in C.G.S System is erg and S.I. System is Joule.